It is a known fact that on the average fluorescent lights consume up to 75% less energy than incandescent lamps with the same light output. The EPA estimates that if Americans were to convert from incandescent lamps to fluorescent, the energy saved would be equivalent to removing 1/3 of all automobiles from the road. Fluorescent lights also have substantially longer service lives, up to ten times the lifespan of incandescent bulbs, and new generations of highly efficient fluorescents with excellent color rendition are being produced in various compact shapes and sizes.
Aside from the considerably higher initial cost, two major hurdles lie in the path of converting incandescent fixtures to fluorescent. First, the fluorescent tube (discharge tube) produces a limited amount of light per linear unit of length, requiring it to be many times longer than the overall length of an incandescent bulb. This requires inventive folding and convoluting to even approach conforming to the same space requirements as incandescents. Some incandescent installations are still too confined to permit upgrading.
Second, the weight and bulk of the conventional magnetic, transformer-style ballast makes it difficult for fluorescents to compete in some installations with the light-weight, compact incandescent. Conventional ballasts have copper wire transformer coils which make it very heavy in addition to being bulky. These limitations have made it difficult to provide a screw-in fluorescent fixture that could be used in a normal incandescent light bulb socket.
With the development of electronic ballasts to replace magnetic, the weight and bulk limitations formerly dictated by the coiled wire ballasts have been partially eliminated. Besides the weight and overall volume restrictions of the ballast, magnetic ballasts also must be provided as a single mass since the coils must be as close as possible to one another for the most efficient transforming. The newer electronic ballasts on the other hand may be arranged and configured to suit more desirable spatial distributions conforming more closely to the space available.
In 1981, Thorn EMI lighting of the United Kingdom launched its 16 watt compact fluorescent lamp line called the 2D lamp series. This lamp is shaped like two letter D's back-to-back, and is somewhat butterfly-like in appearance. The 2D series has been developed from 1981 to the present to include different sizes and different power level fluorescent lamps. The initial 16 watt lamp has been expanded to a line of five different wattage levels ranging from 10 watts to 38 watts.
In addition to the variations in wattage rating and size, some of the 2D lamps incorporate the starter within the lamp support housing, requiring only two pins to connect to a support socket. Others of the lamps do not include the starter and have a 4-prong plug structure for coupling to a mating socket. Because all 4-pin plugs are identical, and all of the 2-pin plugs are identical, with current lamp mounts there is the distinct possibility that lamps of the incorrect wattage will be plugged into available lamp bases. Although there may be coincidental limitations on the available volume due to surrounding structure which would make impossible mistaken use of a large tube in a socket for a small tube, the converse would always be possible. The 10-watt unit will fit all of the other sizes, and would be either immediately burned out, or have a very limited lifespan, if inadvertently plugged into a 38-watt socket.
In addition, although the 2D series is a good, compact design, typically the corresponding base assemblies are not. 2-D goes a long way toward minimizing the limitations inherent in fluorescent tubes, but there has been a failure to maximize the potential of the lamp by distributing the ballast into available, non-invasive space. A typical 2D base assembly, which is described in the specification, requires a space that is of a depth more than twice the depth of the lamp itself to accommodate the bulky ballast.
There is a need for a lamp base assembly which is specifically tailored to the 2D lamp series and which manifests multiple improvements over the prior art lamp base assemblies in both weight and volume and eliminates the possibility of inadvertent power mismatches.